We are trying to run a bank of LTM4650A regulators at the highest ambient temperature possible, ideally approaching 125C . The datasheet states that the maximum junction temperature for this device is 125C. Is there a rule of thumb, or better still a formula, for mapping Junction temperature to ambient temperature? I appreciate that board layout etc will have a significant effect.
With minimum load we recorded a 15C temperature rise of the top of case above ambient. Can this be used to estimate, however roughly, the junction temperature and thus allow us to estimate the max achievable ambient?
Thanks in advance